Now, in the midst of one of the most closely watched investor votes in years — over whether to separate the roles of chairman and chief executive at JPMorgan Chase — that protocol has changed. The firm that is providing tabulations of the JPMorgan vote stopped giving voting snapshots to the proposal’s sponsors last week. The change followed a request from Wall Street’s main lobby group, the firm says.

The pension fund shareholders that are promoting a split at the top of the bank are crying foul. Knowing the current tally is critical for both sides in shaping their campaigns, they say — cutting off access to them gives JPMorgan, which is getting frequent updates, an upper hand.

“They have changed the rules in the middle of the game and it has created an unfair advantage,” said Michael Garland, assistant comptroller who heads corporate governance for the New York City comptroller John Liu. “It’s like playing a game where only the home team gets to know the score.”